pex pipe "grows"

[simonmeridew]

I installed an outdoor boiler this summer/fall and it works great. The only issue that I didn't plan on is that the 1" Pex tubing that I plumbed from the boiler to the heat exchanger is considerably longer than when I installed it. There's  straight sections of hot and return that are  about 40 feet long, and they seem to have "grown" about a foot since the water got hot inside. The boiler temp is running about 170 deg.
I'm thinking I need to reduce a section by maybe 9 inches, but I want to get the length right since I need to shut down the boiler and the tubing is full of water. I don't want to have to do it again.
Any suggestions? What's the expansion per foot or otherwise for this stuff?
simonmeridew

[Ianab]

If you shorten the pipe you may have a problem when you shut the boiler down, the pipe could shrink again.

Maybe put in a couple of 'U' shaped expansion sections in the run. That will let the pipe move as needed with temp changes.

Ian

[thecfarm]

I have heard of steam boilers that use 4 inch metal pipe doing this at a pallet mill,but pex pipe? I put my in last year and have no problems at all and I have 3 heat excahngers and my water temp is about 180-185°.Like they say,I don't understand that at all.Most times with me,if someone will have problems,it's always me.

[farmerdoug]

Pex pipe will difinitly grow and shrink with hot and cold.  It is the nature of plastic piping.  Do not shorten your pex when it is hot or it will pull out when it shrinks as it cools.  You just have to allow for the expansion in your design.  A couple of 90 degree eblow will put the expansion where you want it to be.